Lymph node dissection in small-sized pulmonary metastasectomy: Impact on the long-term survival.

INTRODUCTION: Pulmonary metastasectomy has been clarified in improving long-term survival in most primary malignancies with pulmonary metastasis, while the role of additional lymph node dissection remained controversial. We aimed to investigate the prognosis of lymph node involvement and identify the role of lymph node dissection during pulmonary metastasectomy in a real-world cohort.

METHODS: We identified patients diagnosed with pulmonary metastases with ≤3 cm in size and received pulmonary metastasectomy between 2004 and 2017 in the Surveillance, Epidemiology, and End Results database. We compared the survival via Kaplan-Meier analysis and propensity score matching method, and the multivariable analysis was conducted by cox regression analysis.

RESULTS: A total of 3452 patients were included, of which 2268(65.7%) received lymph node dissection, and the incidence of node-positive was 11.3%(256/2268). In total, the median overall survival was 62.8 months(interquartile range, 28.6-118.9 months), and the lymph node involvement was referred to an impaired survival compared to node-negative diseases(5-year overall survival rate, 58.0% versus 38.6%), with comparable survival between N1 and N2 diseases(P = 0.774). Lymph node dissection was associated with improved survival(HR = 0.80; 95%CI, 0.71-0.90; P < 0.001), and the survival benefits remained regardless of age, sex, the number of metastases, and surgical procedures, even in those with node-negative diseases. At least eight LNDs might lead to a significant improvement in survival, and additional survival benefits might be limited with additional dissected lymph nodes.

CONCLUSIONS: Lymph node involvement was associated with impaired survival, and lymph node dissection during pulmonary metastasectomy could improve long-term survival and more accurate staging.